1. Field of the invention
This invention relates to a data recording method and apparatus for recording digital audio data or computer data on, a tape-shaped recording medium and to a data reproducing method and apparatus for reproducing digital audio data or computer data from a tape-shaped recording medium.
2. Description of the Related Art
There has so far been known a digital audio tape recorder (DAT) for recording digital audio signals on a recording track inclined relative to the running direction of a magnetic tape by a rotary head for the purpose of reducing the length of the magnetic tape required for recording.
Since the DAT can reduce consumption of the magnetic tape and elevate the data rate during recording, it is preferentially used in a tape recorder, known as a data streamer, used for protecting computer data written on a hard disc.
When using the DAT as a tape recorder, data from the host computer is converted into a DAT format data prior to recording.
In the DAT format, a frame is completed by two inclined tracks formed during one complete revolution of two heads having different azimuth angles, and 16-bit PCM audio signals are interleaved and recorded on the frame basis. Each track is made up of 196 blocks, each block being formed by 36 bytes. This track is roughly divided into seven areas, as shown in FIG. 1.
Both end marginal areas M are spare areas for realizing stable contact between the tape and the head. Two sub-data areas are those used for recording subcodes which are a variety of signals, such as time or addresses. Two automatic track finding (ATF) areas are those areas for recording the ATF signals and for achieving automatic track finding via the recording head. A main area D is an area for recording main audio data. In this main area D are recorded the main audio data, error correcting parity and part of the subcodes ancillary to the audio data. The main area D is made up of 128 blocks, each being formed by 36 bytes.
Each of 128 blocks of the main area D has synchronization signals, PCM-IDs, block addresses and a parity, each of one byte, beginning from the leading end of the block. In the next following 32-byte area is arranged main data.
If the data is audio signals, the main data is 16-bit PCM data of the left channel (L) and the right channel (R). This 16-bit main data is interleaved and arranged in the main area of two tracks, that is one frame, along with the parity Q. In this case, approximately 5760 bytes of data are recorded in the main area of one frame.
Since each track is divided in the DAT format into a main area and a sub-area, after-recording can be made using the sub-area.
The structure of the error correction code of main data in the DAT format is the two-dimensional code, as shown in FIG. 3, with the code planes being, four planes per track, each being coded in C1 and C2 directions.
If the DAT is used as a data recorder, data sent from the host computer is 16-bit data handled in the same manner as the above-mentioned PCM data. These data are formatted and recorded in the one-frame main area. In this case, data of the two bytes and 16 bits corresponding to L and R channels are used, and upper four bits thereof are used as format ID, while the lower eight bits are recorded as logical frame numbers. The format ID specifies a format proper to the data recorder. The logical frame number has 23 frames, for example, as a unit, and frame numbers of 1 to 23 are attached on the unit basis.
With the data recorder, employing such DAT, a higher transfer rate and a larger capacity have recently been realized in keeping up with the progress in the format. The data recorder format is prescribed by, for example, the standard of the European Computer manufacturers Association (ECMA). Recently, the recording density is improved by narrowing the track pitch or changing the recording format, such that a data recorder of the third generation has now been prescribed.
The data recorders of the first, second and third generations are termed a DDS (digital data streamer), DDS2 and DDS3, respectively.
Meanwhile, audio data for DAT cannot be recorded at present in a tape cassette for DDS2 nor in a tape cassette for DDS3.
The above-mentioned DDS2 and DDS3 have been utilized as a data recorder for computers, and are not inherently required to have the function of recording or reproducing audio data for DAT. However, if the user in possession of the DDS2 or DDS3 desires to record or reproduce audio data for DAT, it is inconvenient if he or she is compelled to purchase a dedicated recording/reproducing apparatus.